In various fields, notably the automotive field, it is necessary to equip a housing with a rotatable shaft on which have been located a number of mounted elements spaced along its length. In order for the shaft to be rotatably located in bearings arranged in the housing, it is necessary for the shaft to be successively driven through each bearing and each mounted element which has previously been located in position along the path of the shaft.
In the case of such an assembly intended for an application in the automotive field, the composite housing can comprise a cylinder head cover of an automotive engine, the mounted elements being cam lobes for the operation of associated valve mechanisms in the engine. In addition, other elements such as balancing masses can be mounted in order to ensure vibration-free rotation of the shaft.
A previously proposed method of assembling a composite housing fitted with a shaft and associated mounted elements is described in document EP 1 155 770 B. In this document, the described assembly process comprises the steps of: arranging the housing in a predetermined position with respect to an actuator, the housing having at least one opening adapted to receive a shaft; arranging the shaft in a predetermined position with respect to the housing and the actuator; selecting an element to be mounted on the shaft within the housing, the element having an opening adapted to receive the shaft; conveying the element into a predetermined position within the housing, and pushing the shaft by means of the actuator so that it passes successively through the opening in the housing and that in the element to be mounted.
This previously proposed method of assembling a composite housing thus involved locating the elements which were to be mounted on the shaft in predetermined positions corresponding to those they would occupy in the assembled housing, locating the housing around the elements to be mounted on the shaft in a predetermined position corresponding to that it would occupy in the completed assembly, and then pushing the shaft through the openings in the walls of the housing and openings in the elements to be mounted on the shaft, which openings are arranged to be aligned when in the predetermined positions.
In order to ensure a tight fit of the elements on the shaft once the assembly process has been completed, the elements can be heated to a predetermined temperature prior to assembly. This causes the opening in each element to expand and thus facilitate the passage of the shaft. Subsequent cooling causes the opening to contract and thus fix the mounted elements in position on the shaft. In this previously proposed method of assembling a composite housing fitted with a shaft and associated mounted elements, each element was located in its predetermined position some time before the shaft was driven into its assembled position in the housing. This feature presented the disadvantage that, if the elements were heated in advance of the assembly process, the time necessary to locate each element in its predetermined position, added to that required to locate the housing in its predetermined position relative to the elements to be mounted on the shaft, meant that the previously heated elements would have cooled before the assembly process began. The passage of the shaft through the openings in the elements to be mounted would thus be hindered, slowing the assembly process and possibly causing miss-alignment of the various components.